Systems for adaptive equalization of one or more physical channels transmitting a plurality of symbols are well known. See for example, U.S. Pat. No. 6,009,120, issued Dec. 28, 1999, on an application of Nobakht and U.S. Pat. No. 5,539,774, issued Jul. 23, 1996 on an application of Nobakht et al. The Nobakht '120 patent discusses the then prior art involving pulse amplitude modulation wherein all channels tend to introduce noise as well as amplitude and phase distortion that broadens the pulses and causes inter-symbol interference (“ISI”). Two types of interference are discussed, namely, precursor ISI, which is distortion that leads a particular pulse and thus interferes with past pulses and post-cursor ISI, namely, distortion that follows a particular pulse and thus interferes with future pulses. As described in the '120 patent, non-linear equalization, such as decision feedback equalization (“DFE”), was conventionally used to eliminate post-cursor ISI from a given symbol. The '120 patent is directed to a system for equalizing one or more physical channels transmitting a plurality of electrical signals corresponding to a plurality of interdependent symbols according to a multi-dimensional code, wherein a minimum decodable number of symbols is transmitted over more than one symbol interval. ('120 patent, col. 2, lns. 45-52). The '120 patent thus relates to what are sometimes called “interdependent symbols” ('120 patent, col. 4, ln. 15). Equalizers to compensate for the channel distortion on a received pulse are described, for example, in the Nobahkt et al. '774 patent. The '774 patent describes both linear and non-linear equalizers and both “trained” and “blind” equalizers. Nobakht, in the '120 patent, describes the '774 patent as directed to a “signal channel transmitting a sequence of symbols that are sliced and decoded in a strict symbol coded by symbol sequence” ('120 patent, Col. 2, lns. 7 to 10).
The '774 patent proposes using a “trainer” system which communicates with a “trainee” system. On the other hand, the '120 patent is associated with a coded scheme which encodes a plurality of data bits into a multidimensional constellation of data symbols that provides redundancy, gain and noise immunity.
What is desired is an adaptive system which is capable of providing continuous time adaptation without training, and which operates generally, and not just with a multidimensional code utilizing interdependent symbols.